Automobiles and other vehicles normally incorporate suspension systems designed to absorb road shock and other vibrations. Many vehicles are provided with independent suspensions located at each wheel. These suspensions are designed to independently minimize the effect of shock loading on each of the wheels.
Suspension systems commonly employ stabilizer bars which interconnect independent suspensions on opposite wheels, lower control arms, upper control arms or strut assemblies, steering linkage and steering knuckles which are typically interconnected to each other through pivot joints such as ball joint assemblies.
Conventional ball joint assemblies comprise a ball stud seated in a socket. In a suspension link, each end of the link incorporates a socket, and a ball is seated in each socket. The stud, which extends from the ball of the ball joint assembly, is connected to one of the wheel assembly components. Ball joint assemblies allow articulation of the joined suspension components in both an angular and rotational direction through sliding of the joint components. The articulation due to sliding of the joint components offers low-torque rotation, but these designs do not offer shock isolation, since all of the components are typically made from rigid materials such as metal and/or hard plastic.
Another design for the pivot joints is an elastomeric bushing. The elastomeric bushing can be mechanically bonded, it can be chemically bonded during molding or it can be chemically bonded after molding. The elastomeric bushing allows articulation of the suspension components in both an angular and rotational direction through flexing of the elastomeric material. Elastomeric bushings offer excellent shock isolation but they have limited rotational capability because they rely on the flexing of the elastomeric material during rotation. The flexing of the elastomeric material adds a considerate amount of parasitic torque to the pivoting of the suspension and thus leads to a degraded ride performance. In addition, the parasitic torque can complicate the initial assembly of the suspension system.
The continued design for pivot joints includes the development of joint assemblies that offer the advantage of shock isolation but also provide the advantage of low-torque rotation.